PT678124E - PHOSPHATE PROCESSES, PARTICULARLY FOR USE IN THE MANUFACTURE OF PRINTED CIRCUITS USING ORGANIC RESISTORS - Google Patents

Abstract

Composition and methods for providing a phosphate conversion coating on a metal surface, particularly a copper surface, characterized in that the phosphating composition includes at least one composition-soluble compound containing vanadium, niobium, tungsten or tantalum. The phosphate conversion coatings so produced are thicker, more durable and more uniform than those produced by known phosphating compositions. The compositions and processes are especially useful for providing a passivating/uniformizing coating layer on copper surfaces to which organic resin is thereafter deposited to serve as a resist in printed circuit fabrication sequences, particularly when the organic resin is an electrophoretically deposited organic resin. Also described is the microetching of copper surfaces with a phosphoric acid/peroxide microetchant preparatory to deposit thereon (or after a further provision of a phosphate conversion coating) of a photoresist which is then imagewise exposed and developed to provide a patterned resist.

Description

naked

FIELD OF THE INVENTION 1. Field of the Invention The invention relates to a process for the preparation of a pharmaceutical composition comprising a pharmaceutical composition comprising a pharmaceutically acceptable carrier. The present invention relates to a process for providing phosphate conversion coatings on metallic copper surfaces and the use of such process in connection with sequences for the manufacture of printed circuit boards employing organic resistances and more particularly sequences in which are used as resistances organic resins deposited electrophoretically. Obtaining phosphate conversion coatings on metal surfaces is a well known surface treatment procedure. Such coatings which are formed in situ on the surface of the metal substrate and incorporate surface dissolved metal ions are known for use as sub-coatings for applied paints, for example in zinc or iron or aluminum, as well as for use in forming or aiding the formation of corrosion resistant surfaces. Typical commercial phosphating compositions comprise one or more metal phosphates (e.g., alkali metal phosphates) dissolved in phosphoric acid. EP 0015020 discloses a phosphating liquid which includes an additive chosen from molybdate, tungstate, vanadate, niobate and tantalate ions. 1

EP 0305560 discloses a surface of metal particles treated with an aqueous solution containing phosphate ions, soluble vanadium ions and oxygen.

A recent advance in the manufacture of printed circuit boards also uses phosphate conversion coatings to passivate and uniformize the copper surfaces prior to the electrophoretic deposition thereon of organic resins to serve as resistance (e.g., recording resistors, electrolysis resistors) in sequences manufacture of printed circuits. This advancement resulted from the recognition of fundamental problems encountered in the known use of electrophoretically depositable organic resins as resistances on copper surfaces such as localized insufficient protection of the copper recording surface when the resins are used as recording resistors and imaging properties and developmental and inconsistent when the resins are applied as photoresist. In turn, these problems were found to be attributable to substantial lack of uniformity of thickness, density and consolidation of the deposited resin layer. In addition, it has been found that this non-uniformity could be attributed to non-uniform random oxidation of the exposed copper surfaces on which the resins are applied in the manufacture of the printed circuit boards. At the moment of electrophoretic deposition, copper surfaces exhibit substantial characteristics of lack of uniformity in resistivity / conductivity; since the rate of electrophoretic deposition is proportional to the voltage difference between the applied voltage and that of the surface on which it is being deposited, the non-uniformity properties of the copper surface to point resistivity / conductivity can give rise to a substantial lack of uniformity of thickness, density and consolidation of the layer of resin applied thereto. In extreme cases, the deposited resin layer can be so thin in localized areas (some 2

times to the extent of being essentially non-existent as in the form of a peak defect) in order to provide insufficient protection of the underlying copper surface (for example against recording solutions), or may be so thick in localized areas that render imaging and development impossible to provide the intended resistor models. The recent advance in this regard involves forming on the copper surfaces, prior to the electrophoretic deposition of the organic resin thereon, of a uniformization / passivation coating, i.e., a coating that passively surfaces copper surfaces against non-uniform random oxidation and which substantially uniformizes the surfaces with respect to their resistivity / conductivity characteristics. In this way, it becomes possible to apply to these surfaces a layer of resin electrophoretically deposited thereon which, in its thickness, density and consolidation properties, is of the uniformity that is required for the resistances in printed circuit manufacturing sequences. Such a passivation / uniformisation coating useful for the copper surfaces is a phosphate conversion coating.

As a further work on this recent advance in the manufacture of printed circuits, it was determined that further refinement could be obtained if the phosphate conversion coating itself could be improved in its ability to passivate the surfaces of copper foams and in their ability to provide surfaces of uniform resistivity / conductivity characteristics for the subsequent electrophoretic deposition of the resin thereon to serve as resistance in the manufacture of printed circuit boards. Specifically, it has been found that known phosphate conversion coating compositions and phosphating processes 3

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often provide only a minimum conversion coating on the copper surfaces. While even obtaining only a minimal phosphate conversion coating is very useful in the manufacture of printed circuits using resins electrophoretically deposited as resistors (i.e., obtaining a far more uniform and passivated surface for such deposition compared with in which case the phosphate conversion coating is not used), the general process improvement and process control can be achieved if phosphating compositions and processes are consistently produced which provide a more phosphate conversion coating the copper surfaces.

In view of this specific need, novel phosphating compositions and processes have been developed which have particular utility in the preparation of passivation / uniformization coatings on copper surfaces in which organic resins are electrophoretically applied in order to serve as resistances in the circuit manufacturing processes printed. Even better, the phosphating compositions and processes thus developed have utility in all environments where phosphate conversion coatings are traditionally employed. The main object of the present invention is to provide processes for the production of phosphate conversion coatings on copper surfaces.

Yet another object of the invention is to provide processes which on copper surfaces produce a phosphate conversion coating which is thicker, more durable and more uniform than has hitherto been possible using known methods.

Furthermore, it is still an object of the invention to provide phosphatization processes for converting copper surfaces into 4 V.

or surfaces which are substantially passive to the oxidation and which are substantially uniform in their resistivity / conductivity characteristics.

A further object of the invention is to provide processes for the manufacture of printed circuits wherein a phosphate conversion coating is formed on copper surfaces prior to the application of the organic strength thereto, particularly when the strength is provided as an electrophoretically deposited organic resin .

These and other objects, of course, are achieved by applying a method for producing a phosphate conversion coating on a copper surface used in forming printed circuits, which process comprises contacting the copper surface with the composition aqueous phosphating agent for a time effective to produce a phosphate conversion coating on the copper surface, wherein the aqueous phosphating composition, in addition to the essential components of a phosphating composition per se, comprises at least one compound soluble in the composition of an element selected from the group consisting of vanadium, niobium, tungsten and tannan. The phosphate conversion coatings produced on the copper surfaces by means of these compositions are characterized by improved thickness, improved durability and improved overall uniformity, including uniformity of resistivity / conductivity characteristics. As a consequence, the compositions provide on the copper surfaces a phosphate conversion coating which is ideally suitable for electrophoretic deposition on such organic resin surfaces for use as a strength in a printed circuit manufacturing process and which is also suitable for a certain number of other purposes.

Typically, the composition-soluble vanadium, niobium, tungsten or tantalum compound is a compound in which the element 5 is present as part of (and usually serving as the central element of) an oxoanion, such as the vanadates (e.g., VO 3 " (For example, NaOH), and tantalates (for example TaO3), and more typically in association with an alkali metal element or an alkali metal element, as a cation (eg sodium, potassium, etc.)

In addition to the above-mentioned compounds, the aqueous composition will contain the typical major components of the traditional phosphating compositions, in particular phosphoric acid, and may further contain any known additives for the compositions which perform functions as sources of phosphate ion and / or pH or buffering agents and / or accelerators to accelerate the conversion reaction (eg nitrites, nitrates, chlorates, peroxides and the like) and / or sources of other metals soluble in the composition. To produce the phosphate conversion coating, the applicable copper surfaces (which as used herein include copper alloys or copper intermetallic compositions) are brought into contact with the composition such as by immersion or spray , for the time required to provide the phosphate conversion coating of acceptable thickness, typically requiring a time of from about 10 seconds to about 10 minutes depending on the particular composition and its temperature (ranging from about 15 ° C (60øF) to about 93øC (200øF), more typically 49øC (120øF) to 71øC (160øF).

As noted, the invention also provides improved processes for the manufacture of printed circuits, which processes are of the general type in which an organic strength is applied on a copper surface and more particularly in manufacturing processes in which an organic resin is electrophoretically deposited on a copper surface to serve as a resistor (for example, coating resistance, recording resistance). In improved processes, the copper surfaces prior to the application of the organic strength thereon are first provided with a substantially uniform layer of a phosphate conversion coating using the process of the invention and then the organic strength is applied over the phosphate conversion coating.

As discussed previously, an important aspect of the present invention is to provide printed circuit fabrication processes using electrophoretically deposited organic resins as chosen copper surface resistances, the process of the invention being used to provide a passivation / surfaces prior to the electrophoretic deposition of the resin thereon. Accordingly, the invention is first described with reference to this environment for its use.

In the manufacture of printed circuits, the use of organic resistances in the manufacturing sequence is well known. For example, organic resistances are often provided with a preselected configuration on a copper-covered dielectric substrate to serve as selective electrolysis resistance, whereby in a subsequent metallization step, only the uncovered copper areas are metallized resistance material. Also well known is the adoption of organic resistors in a preselected configuration on a copper-covered dielectric substrate to serve as selective attack resistance, wherein a subsequent step selectively attacks only the copper areas not covered by the resist material. The desired configuration of the organic strength can be achieved by selectively applying the composition of the copper surface resistance by means of a suitably configured mask or by photographic imaging techniques. Finally, the photoactive resistor composition is applied as a layer to the copper surface and then exposed, image by image, to the appropriate wavelength activation radiation through a mask. Depending on the nature of the photoactive composition, i.e. if it works as a positive or works as negative, subsequent disclosure of the composition will result in subsequent obtaining on the copper surface of a configuration of the organic resistance corresponding to the negative or the positive, as where appropriate, of the exposure setting to light. It is also known that, as organic resistances, compositions can be employed which can be deposited electrophoretically on conductive surfaces (i.e., copper). These resistor compositions may be photoactive or non-photoactive. For the former, electrophoretic deposition is used to provide a layer of the composition on the copper surface, whereupon the exposure to light from image to image and the development result in the configuration of the desired organic resistance. For the latter, the surface in question is already present in a configuration of conductive and non-conductive surfaces (such as in the case where a copper surface has previously been selectively configured with an electrolysis resistance that remains temporarily in place), and electrophoretic deposition of the resistance results in its selective application only to the exposed conductive surfaces. The use of electrophoretically depositable resins as resistors in the manufacture of printed circuit boards has a number of advantages for the manufacturer. By their nature they are capable of selective deposition only only if the exposed conductive surfaces of a substrate already configured on conductive and non-conductive surfaces and thus provide the manufacturer with an easy means for selectively depositing resin to serve, for example , as a recording resistance for the copper areas that lie below the manufacturing sequence. Even when the selective deposition property is not required, such as when the resin is a photoactive resin which will simply be deposited as a layer and subsequently exposed and developed to obtain a configuration, electrophoretic deposition provides an easy medium curl coating, etc.) to deposit the resin layer and particularly to provide the resin in the form of a very thin layer (for example, 0.005 to 0.01 mm (0.2 to 0.5 mil) of thickness) suitable when very thin line circuit strokes are desired.

In the recent advancement of this previously discussed technique, it has been found that for all situations where in the course of fabricating a printed circuit in which an organic resin is to be deposited electrophoretically on a copper surface to serve as a resistor, a significant advantage if the copper surface is preliminarily treated to provide a phosphate conversion coating thereon, over which the organic resin is then deposited electrophoretically. In the present invention, a further improvement is further realized and the corresponding advantage is obtained by use of a particular phosphate conversion coating, i.e. a coating provided by a phosphating composition containing at least one compound soluble in the solution having an element selected from the group consisting of vanadium, niobium, tungsten and tantalum.

As with the recent advancement of the art, the improved process of the present invention is applicable in any or all situations in the course of making printed circuitry wherein an organic resin is to be deposited on a copper surface by electrophoresis 9

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to serve as a resistance. Although there are a large number of different processes for the manufacture of printed circuits using resistances on copper surfaces, some processes are discussed below as examples indicative of the breadth of application of the improved technique.

In the manufacture of printed circuit boards which contain metallized side-by-side holes, as is generally the case in the manufacture of the inner layer circuits for later use in the manufacture of a multilayer printed circuit, the starting material is a dielectric substrate material which has a copper coating on it (typically in the form of a plated copper sheet attached to the surface of the dielectric substrate). The desired configuration of the conductor circuits is achieved through the use of photographic imaging and recording techniques. In the context of electrophoretic deposition, then, an electrophoretically depositable organic resin composition and with which photographic images can be formed is deposited in a layer on the copper surface by electrophoresis. The layer is then photographed and developed to produce a resistance with the desired circuit configuration. Thereafter, the carton is subjected to a copper etching process in such a way that all the copper not protected by the etching resistor is withdrawn to the surface of the substrate. After removal of the recording resistor, copper is set to the desired setting.

In such known processes, the copper surfaces on which the photoresist layer is to be applied electrophoretically are preliminarily cleaned to remove contaminants prior to electrophoretic deposition, for example by cleaning to remove organic contaminants, micro-etch and / or abrasion mechanical means for removing inorganic contaminants such as oxides and the like. According to the recent advancement of this technique described above, it has been found that in these processes the known, electrophoretically depositable electrophoretic photoresist layer so often applied is of non-uniform thickness or otherwise. non-uniform properties, often even to the point of having fine hole formation defects. It has been hypothesized that this lack of uniformity results from the fact that the surface of the clean copper in which the resin is deposited electrophoretically is thermodynamically very unstable and thus undergoes rapid and non-uniform surface oxidation before the resistance layer can be electrophoretically deposited thereon. As a result, the surface on which the resistance layer is deposited is not physically uniform or uniform in its conductivity / resistivity and the resistance layer deposited thereon is also non-uniform in thickness or other properties. In this particular situation, i.e. where electrophoretically deposited photosensitive resin is used as a recording resistor, there are at least two disadvantageous consequences of this lack of uniformity of the resin layer. First of all, problems in the time and / or in the conditions necessary to carry out the image exposure and the developing image necessary to provide the desired recording resistance configuration may be encountered. Second, as far as the recording resistance thus produced is concerned, its non-uniformity may result in obtaining certain areas which provide insufficient protection to the copper areas that lie below during the copper engraving operation (particularly this it is thus if non-uniformity involves or includes defects of fine holes); undesired recording of areas of copper may, of course, lead to openings, short circuits, or other defects.

In the recent advancement of the art, in which the process of the present invention provides improvements, the copper surfaces in which the photoinformable resin layer is intended to be electrophoretically applied in the above-mentioned manufacturing process are

II are first treated to provide a phosphate conversion coating. In addition to thereby passivating the copper surfaces so as to avoid any random non-uniform oxidation prior to electrophoretic deposition of the resin, the phosphate conversion coating thus formed renders the overall surface more uniform both physically and in terms of its conductivity / thereby allowing the electrophoretically deposited resin to also be deposited as a substantially uniform, substantially undefended layer, thereby avoiding the above-described problems with the non-uniform resin layers. Following the application of the resin layer by electrophoresis on the phosphate conversion coating on the copper surfaces and the formation and imaging, the non-protected copper areas are then chemically attacked to the surface of the substrate. The most commonly used copper dissolution reagents are also effective in dissolving the phosphate layer on copper. Obtaining a phosphate conversion layer on copper surfaces on which a resistor is electrophoretically deposited in accordance with the recent advancement in the art and with the present improvements has applicability in any number of printed circuit manufacturing processes employing resistors or as electrolysis and / or etching resistors, and whether or not the resistor is a resistor which is produced by forming photographic images.

By way of further examples on this subject, the invention is also applicable in processes for the manufacture of printed circuit boards containing metallized side-by-side holes such as for printed circuit boards on both sides; layers of circuits in the outer phase of multilayer printed circuits 12; and inner layer circuits for multilayer printed circuits which have to be passed through holes. In a typical process of this type, the copper plated or multilayer composite dielectric has side-to-side orifices and the orifices are metalized by, for example, copper deposition without the use of electricity. The side-by-side holes are plated with copper without electricity and the surfaces of the sheets can still be constructed of copper thickness by depositing more copper without using electricity, or more typically of electrolytically copper. For this purpose, the plate is provided with a photographic image to provide a configuration of the resistance formed by electrolysis thereon (i.e., in the negative of the areas of the desired circuits) before the additional electrolytic coating in order to avoid areas of copper obtained by electrolysis which eventually have to be chemically attacked. In the context of the present invention, the resistance thus employed may, if so desired, be a resistance obtained electrophoretically by forming a depositable photographic image which is applied as a layer on the copper surfaces without electricity and then exposed image and developed by regulated image. By first applying over the copper surfaces without electricity a uniform phosphate conversion coating according to the invention, the resin layer is electrophoretically depositable as a layer of substantially uniform thickness, with the concomitant advantage of uniformity in the forming operations of image and revelation.

Regardless of the resistance used as electrolytic coating resistance (i.e., electrophoretically deposited, dry film, liquid photoresist), the areas below the resistor are then chemically attacked without the covered copper areas being attacked and forming the copper circuitry. For this 13

Lc. ), The electrophoretically depositable etching resistors are ideally suitable since they can be selectively applied to the accumulated copper areas and not over the coating resistance in much the same way as is possible with the electrocoated tin resistors and / or lead attack techniques conventionally employed in the art. Obviously, for this purpose the electrophoretically depositable organic strength need not be obtained by photoimaging. According to the invention, the accumulated copper areas are first provided with a uniform phosphate conversion coating before the etch resistance is electrophoretically applied thereto, thereby allowing the deposition of a resistance of uniform thickness and properties substantially without any pruning defects. The resistance is thus to protect the accumulated copper against the chemical attack. Following electrophoretic deposition of attack resistance, the coating resistance is withdrawn and the copper underneath is tacked up to the surface of the substrate. Thereafter, the attack resistance can be removed, leaving the desired surface configuration of copper circuit covered.

The phosphating compositions which are used to provide the desired phosphate conversion coating on the copper surfaces in these printed circuit fabrication sequences comprise aqueous solutions whose key ingredient, in addition to phosphoric acid per se, is a compound soluble in the composition a mixture of such compounds) of an element selected from the group consisting of vanadium, niobium, tungsten and tantalum, more typically and preferably a compound wherein the element is the central element of an oxoanion, such as vanadates, niobates, tungstates and tantalates. Most preferred are the compounds employing 14 ν

an alkali metal or alkaline earth metal such as cation such as NaV03, Na3 CO4, K2 WO4, NaNb03, NaTa03 and the like.

In other words, the compositions used in the process according to the present invention may be those which result simply from the incorporation of a compound or mixtures of vanadium, niobium, tungsten or tantalum compounds soluble in the composition, in any known composition to provide a coating of phosphate conversion on the copper surfaces. More typically, such known compositions are based on buffered phosphoric acid solutions, as numerous optional ingredients to obtain the particular processing or the advantages or effects of the coating and the improvement is in this case in the inclusion of the compound of V, W, Nb or In these compositions. In this regard reference may be had to the indications, for example, of U.S. Patents 2,233,462; 2,772,216; 3,269,877; 3,645,797; 3 764 400 and 3 833 433, for known phosphating compositions for copper and the indications are expressly incorporated herein by reference. Reference may also be made to Volume 15, pages 301-309, Kirk-Othmer Encyclopedia of Chemical Technology, (3rd ed. 1981), also incorporated by reference herein.

Typically, the concentration of the compound soluble vanadium, niobium, tungsten or tantalum compound or compounds in the composition in the phosphating composition will be in the order of magnitude of about 0.1 to about 200 g / l, more preferably about 1 to about 50 g / l and more preferably from about 1 to about 5 g / l. The compositions are typically acidic, and preferably have a pH range of about 1 to about 6, more preferably about 4 to about 6.

Copper surfaces contacted by the phosphating composition to provide the required conversion coating of the required phosphate are typically cleaned prior to such contacting to remove contaminants from the surfaces such as organic compounds, oxides and the like, by means of solutions (e.g. peroxide / sulfuric acid solutions) and, less preferably, mechanical scrubbing or abrasion techniques. Thereafter, the copper surfaces should be washed and contacted with the phosphating composition as soon as possible. Following the formation of the phosphate conversion coating according to this invention, the entire substrate will typically be washed with water before the strength material is deposited electrophoretically on the surfaces of the copper to be applied. While it is generally good practice to avoid long retention periods between the formation of the phosphate conversion coating and the deposition of the resistance, it is a distinct advantage of this invention that, since the phosphate conversion coating serves to passivate the copper surfaces against subsequent formation of random oxide in the air, the time interval between the controlled formation of the uniform phosphate conversion coating and the time at which the resistance is to be deposited is greatly increased. The electrophoretic deposition of the strength on the uniform copper surfaces (having a phosphate conversion coating) may be carried out with any suitable electrophoretically depositable organic resin and under any suitable deposition conditions known in the art. As already mentioned, depending on the printed circuit fabrication sequence, the electrophoretic deposition may be made in such a way that a layer of a photoactive resin is deposited (which is then exposed to light and developed to produce the desired strength configuration for use as a coating or etching resistor) or for selectively and as a directly depositing resin (for example etching resistor) on the conductive surfaces of a carton having an existing configuration of conductive and non-conductive surfaces.

In general, electrophoretic deposition takes place in a cell containing a solution or emulsion of the organic resin and more typically, the copper surfaces on which the phosphate conversion coating formed form the cathode in the cell (positively charged organic resin). The temperature at which the electrophoretic deposition takes place is generally between about 70Â ° F (21Â ° C) and about 38Â ° C (100Â ° F), and the tension typically ranges from about 20 to about 300 volts. The electrophoretic deposition of the resin continues until the desired resin thickness is obtained. Generally, the thickness will be of the. order of magnitude from about 0.005 to about 0.05 mm (about 0.2 to about 2.0 mil) depending on the type of strength (eg coating or etching) and the type of circuits involved, but any optimum and desired thickness can be employed.

For other particularities relating to electrophoretic resin coatings in the specific context of the printed circuit manufacturing sequences, reference may be made to USSR Inventor Certificate No. 293 312 (published May 10, 1971); British Patent Specification No. 1 194 826 (published June 10, 1970); French Patent Application 2,442,732;

U.S. Patent Nos. 3,892,646 to Lazzarini et al .; 4,992,816 to Emmons et al .; 4,746,399 to Demmer et al .; 4,751,172 to Rodriquez et al .; and 4,861,438 to Banks et al. The foregoing references and particularly the extensive discussion in a large number of the various types of polymer resins that can be deposited by electrophoresis (for example, cationic polymers depositable on the surface of a negatively charged substrate (cataphoresis) and anionic polymers deposited on the surface of a positively charged substrate (anaphase)), are incorporated herein by reference.

As noted at the outset, the advantage of the phosphatization compositions used in the invention in this context of the printed circuit manufacturing sequences using electrophoretically deposited organic resins as resistances for copper surfaces is that the compositions consistently provide phosphate conversion coatings which are thicker, more durable and more uniform (particularly resistivity / conductivity characteristics) than has hitherto been possible using known phosphating compositions. As a consequence, the coated copper surfaces on which an organic resin to be deposited electrophoretically to serve as a resistor are strongly passivated against any random non-uniform oxidation phenomena prior to the application of the resin by electrophoresis and are very uniform in the resistivity / conductivity characteristics , thereby resulting in a deposit of the strength which is very uniform with respect to its thickness, density and consolidation properties and thus has the characteristics required for resistances in the printed circuit manufacturing sequences.

These same features and advantages of the phosphating composition used in the invention, i.e., producing a phosphate conversion coating on copper which is thicker, more durable and more uniform than has hitherto been possible, also render the compositions extremely useful in any situation where it is desired to obtain a copper surface with a phosphate conversion coating for any purpose, either to improve adhesion to the copper surfaces of permanent coatings, or to improve the corrosion resistance of copper surfaces or the like. 18

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In particular, the improved phosphate conversion coatings used in the present invention offer advantage in any printed circuit fabrication sequence wherein an organic resistance obtained by photographic images is used in order to provide a configuration of the resistance, i.e. including situations wherein the photoresist is not applied by electrophoretic deposition, but is preferably, for example, a dry film strength or a liquid photoresist applied by roller coating, curtain coating, sieving or the like.

In such processes, the key feature is the application of the photoresist composition to surfaces which are either completely copper or include areas of copper in the form, for example, of a uniform layer, followed by selective exposure similar to photography and configuration of the desired resistance. For the process, it is critical that during development the complete removal of the photoresist composition from areas where no resistance is desired; depending on the sequence of the printed circuitry in question, if unintended strength is maintained thereafter, areas of copper which, for example, are assumed to receive a subsequent metal coating will not be coated or areas of which copper is supposed to be attacked, attack solution.

Problems are often encountered in this regard because the applied strength composition adheres very tenaciously to the copper surfaces on which it is applied to the extent that its intended removal in the developing operation after exposure to light similar to the photographic images chosen, does not occur or occurs only with difficulty. According to the invention, preliminarily providing copper surfaces on which the photoresist is to apply a phosphate conversion coating of the invention prior to the application of the 19 V.

photoresistance, the copper surfaces are transformed into surfaces that are very uniform and relatively smooth. The photoresist applied on these surfaces and exposed in a manner similar to the formation of photographic and revealed images, has been found to develop very cleanly without the need for overly tight developing conditions and without compromise of adhesion of the resistance on the chosen copper surfaces which are intended to remain. The invention is further illustrated and described with reference to the following examples.

EXAMPLE I

In this example, the improved phosphating composition is employed to produce a phosphate conversion coating on the copper surfaces prior to deposition thereon by organic resin electrophoresis to serve as a strength in a printed circuit manufacturing process compared to the same process using conventional phosphating composition.

A laminate having a central portion of epoxy resin reinforced and plated with copper foil was processed as follows: 1. The surfaces of the copper foil are cleaned of organic impurities by soaking it in a commercial cleaning agent [Metex T- 103 to 75 g / l; MacDermid, Inc.] for 3 minutes at a temperature of about 60-71Â ° C (140-160Â ° F), followed by washing with water. 2. The sheet surfaces were then microdipped with a peroxide / sulfur solution [MACuPREP ETCH G-5; MacDermid, Inc.] for about 2 minutes at a temperature of about 27øC (80øF) (removal of about 1.27

μιη (50 microinches) of copper), followed by washing with water. 3. The paperboard was then dipped in a conventional phosphating solution containing 17.6 g / l phosphoric acid, 6.9 g / l Na2 CO3 and 0.5 g / l Na2MoO < (pH = 5.0-5.5) for about 3 minutes at a temperature of about 65 ° C (150 ° F), to provide a phosphate conversion coating on the surfaces of the copper foil followed by washing with water. 4. A 0.01 mm (0.4 mil) thick layer of photosensitive organic resin (Electro-Image 1000R; PPG Industries) was then cataphoretically deposited on the phosphate conversion coating surfaces using approximately a tensile strength of 200 volt for 30 seconds. Following drying, the resin layer was exposed in a photograph-like manner to the activation radiation and developed to produce a resin etch resistant configuration. 5. Phosphate coated copper surfaces not protected by the strength configuration were tacked to the dielectric layer using an ammonia etching agent [ULTRA ETCH 50; MacDermid, Inc.], followed by resistance runoff and washing and drying of the laminate. Inspection of the thus processed laminate revealed that the strength was fairly uniform in thickness, density and consolidation and served to adequately protect the underlying copper surfaces against pickling, particularly when compared to an identical process but without any coating formation of phosphate. Nevertheless, it was determined that the applied resistance was not as uniform as it could be, at least in theory. X-Ray Fluorescence Energy Scattering Spectroscopy (EDACS) analysis of a copper surface sample processed by the first three operations of sequence 21

U previously disclosed in fact revealed that only a minimum conversion coating had been made (i.e. very little phosphorus was present on the copper surface) and that the coating itself was not entirely uniform.

Another copper-plated epoxy laminate was then processed in the same manner as described in the above five operations, but adding 1,0 g / l of sodium vanadate (NaV03) to the phosphating composition. Inspection of the thus processed laminate revealed that the applied strength was extremely uniform in its thickness (no more than + 1 micrometer of thickness variation), density and consolidation. EDACS analysis of a copper surface sample processed by the first three operations of the sequence has shown that a much thicker and more uniform continuous phosphate conversion coating can be produced than if the conventional phosphating composition is used.

As noted above and is reflected in the foregoing example, copper surfaces which are to be provided with a phosphate conversion coating according to the typical invention and preferably will first be cleaned and microdecapped prior to contact with the phosphating composition, the microattack typically being carried out using a traditional microattack composition, for example peroxide / sulfuric acid solution. According to a preferred aspect of the invention, it has been found that further advantages can be obtained by using as the microdroplet composition of the copper a solution of phosphoric acid / peroxide, preferably a conventional microdroplet composition sulfuric acid / peroxide. Particularly when the copper surfaces are chemically micro-treated in this way followed by the formation of the phosphate conversion coating on them in accordance with the invention, followed by application to the surfaces of a photoresist composition which

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u, requires exposure to radiation similar to the formation of photography and development, the development occurs even more easily and in an extremely clean way so that there is no unwanted resistance in areas of which it is intended to be removed in the disclosure and without commitment of the adhesion of the resistance to the chosen copper surfaces and that the resistance is intended to be maintained.

In this embodiment of the invention, the microdecorative composition comprises an aqueous solution preferably containing 2-15 wt.% Of phosphoric acid (based on a 85% phosphoric acid storage solution), more preferably 5-10 wt.%, And 0.5-15% by weight of peroxide (based on a 50% hydrogen peroxide storage solution), more preferably 3-5% by weight, together with optional peroxide stabilizing agents and / or enhancement agents chemical compositions as are known in the art as sulfuric acid / peroxide microdroplet compositions and used under essentially the same conditions as are known for conventional sulfuric / peroxide acid microdroplet compositions.

This aspect of the invention is illustrated in the following example in connection with an electrophoretically deposited photo-impressionable organic resin.

EXAMPLE II

A laminate having a copper foil-reinforced epoxy resin core was processed according to Example I of the invention (i.e., using the phosphating composition containing 1.0 g / l sodium vanadate added ), but with the substitution in step 2 of the MACuPREP ETCH G-5 microdecapper by a microdecapping composition containing 8% by volume of 85% phosphoric acid and 3% by volume of 50% microdecaptive hydrogen peroxide.

After the disclosure, the non-exposed radiation resistance composition was exceptionally easy to remove in a uniform manner, with no incidence of unwanted residual resistance. While complete removal of the resistance during development and in the comparative sequence can be accomplished using the sulfuric acid / peroxide copper microdecaptive composition, the improved sequence using the phosphoric acid / peroxide microtack composition was slightly more resistant to failure in that regard and did not require any special care or attention for the post-development removal as may be the case in sequences using the conventional microdecorative composition. The above-mentioned preliminary preparation of the copper surfaces prior to the application of a phosphate conversion coating and a photoresist composition causes removal of the improved strength during the development even in situations where a conventional phosphating composition is employed, a composition without the presence of the vanadium, niobium, tungsten and / or tantalum compound as in accordance with the present invention. Thus, while improved phosphating compositions are evidently preferred, particularly to arrive at exceptionally uniform surfaces leading to obtaining electrophoretically deposited organic resins which are highly uniform in thickness, density and consolidation, the facilitated removal of the resistance during development regardless of the phosphating composition employed.

Still further in this regard, it has been determined that the treatment of copper surfaces with the microdecaptive phosphoric acid / peroxide composition has advantage over the application and disclosure of a photoresist composition, even in situations where the photoresist composition is applied directly onto the microdipped surfaces, i.e. without first providing the phosphate conversion coating on the copper surface. This is particularly so when the photoresist u

V r is not a photoresist that is applied by means of electrophoretic deposition.

This treatment is applicable to any printed circuit manufacturing process wherein a photoresist composition is applied to copper surfaces followed by exposure for imaging and developing the composition so as to selectively remove the composition from the chosen copper surface areas and leave the desired resistance setting. In such processes, the copper surfaces on which the photoresist composition is applied are microdissetted with the phosphoric acid / peroxide microcatcher composition and the photoresist composition is then applied directly onto the thus-exploited copper surfaces. Compared with an identical sequence but using a conventional microdroplet composition of sulfuric acid / peroxide for copper, it has been found that the removal of the copper surfaces from the chosen portions of the photoresist during the development is greatly facilitated, i.e., without incidence or with little reliance on situations where the composition adheres so tenaciously to the copper surface that it makes removal difficult or there is a risk of leaving resistance in areas where it is unwanted.

As noted, this is particularly well suited for the printed circuit fabrication sequences or portions of those sequences in which the photoresist composition is different from that applied by electrophoretic deposition, such as for dry film photoresist or liquid resistance applied by, for example , roller coating, curtain coating, sieving or other similar method, since for these photoresists it is not critical that the copper surfaces on which they are applied exhibit the uniformity of resistivity / conductivity properties which is ideally required for the compositions of resistance and which can be accomplished by the phosphate conversion coating application 25 prior to the electrophoretic deposition of the resin. The above is illustrated in the following reference example which is not according to the present invention.

EXAMPLE OF REFERENCE III

A laminate having the epoxy resin interior reinforced and plated with copper foil was processed according to Operations 1 and 2 of the sequence referred to in Example I, followed by lamination with the microdipped copper foil of a dry film photoresist and exposure similar to photography and revelation of photoresistance. Another laminate was processed identically but with the use in Operation 2 of a copper microdroplet composition containing 8% by volume of 85% phosphoric acid and 3% by volume of 50% hydrogen peroxide (i.e. instead of the composition sulfuric acid / peroxide MACuPREP ETCH G-5). In comparison, the sequence using the phosphoric acid / peroxide microdecapping composition showed a greater ease of removal and a cleaner removal of the unexposed photoresist during the developing operation.

It should be noted that the foregoing statement is provided in the description and illustration of the invention and its preferred embodiments and is not intended to limit the scope of the invention as defined by the appended claims.

Lisbon, August 22, 2000 THE OFFICIAL AGENT OF INDUSTRIAL PROPERTY 1

26

Claims (14)

V A process for the production of a phosphate conversion coating on a copper surface used in forming printed circuit boards, which process comprises contacting the copper surface with an aqueous phosphating composition for a time effective to produce a phosphate conversion coating on the copper surface, characterized in that the phosphating composition comprises at least one compound soluble in the composition containing a selected element of vanadium, niobium, tungsten and tantalum. Process according to claim 1, characterized in that the contact is carried out for a time in the range of about 10 seconds to about 10 minutes. A process according to claim 1 or claim 2, characterized in that the temperature of the aqueous phosphating composition is from about 60Â ° F (16Â ° C) to about 200Â ° F (93Â ° C). A process according to any of the preceding claims, characterized in that the compound soluble in the composition is present in the aqueous phosphating composition at a concentration of from about 0.1 g / l to about 200 g / l. A process according to any of the preceding claims, characterized in that the compound soluble in the composition contains an oxoanion of said element. 1 A process according to claim 5, wherein the compound soluble in the composition is a vanadate, a niobate, a tungstate, a tantalate or a combination thereof. A process according to claim 6, characterized in that the compound soluble in the composition is an alkali metal vanadate. A process for the manufacture of printed circuits, wherein an organic resin is deposited on a copper surface to serve as a strength in the process, which method comprises the steps of applying to the copper surface a substantially uniform layer of a conversion coating of. phosphate by a process as defined in any of the preceding claims and then depositing the organic resin on the phosphate conversion coating. A process according to claim 8, characterized in that the organic resin is an electrophoretically depositable resin and is deposited electrophoretically above said phosphate conversion coating. A process according to claim 8 or claim 9, characterized in that the organic resin is photoactive and is exposed in a manner similar to a photographic image and developed to serve as a resistor. A process according to claim 10, characterized in that the photoactive organic resin is a dry film photoresist. A process according to any one of claims 8 to 11, characterized in that the copper surface on which the phosphate conversion coating is formed is a copper foil attached to a substrate surface. A process according to any of claims 8 to 12, characterized in that the copper surface is micro-de-capped prior to the formation of the phosphate conversion coating thereon. A process according to claim 13, characterized in that the copper surface is microdipped by contact with an aqueous solution comprising phosphoric acid and hydrogen peroxide. Lisbon, August 22, 2000 0 OFFICIAL AGENT OF INDUSTRIAL PROPERTY u 3